1. Field of the Invention
The present invention relates to a cylinder head gasket in an internal combustion engine. More particularly, it relates to a cylinder head gasket having a construction wherein a core of a metal material in the form of a web contains hooks.
2. Description of the Related Art
In general, the construction of a cylinder head gasket for an internal combustion engine includes three layers comprising a core of metal material and gasket plates made of a heat-resistant sealing material, such as asbestos or graphite, and connected to respective sides of the metal core by applying pressure. The gasket also has, at the periphery of openings corresponding to cylinder bores of the engine, grommets fitted to the gasket plates in order to obtain a good sealing effect.
In Japanese Non-examined Utility Model Publication (Kokai) No. 56-127349, an improved cylinder head gasket is proposed wherein the steel web forming the material of the metal core is provided with a plurality of hooks arranged thereon to permit the steel web to be sealingly engaged with the heat resistant seal material. These hooks also serve to increase the rigidity of the cylinder head gasket as a whole. Therefore, the improved cylinder head gasket is particularly suitable for an engine having a high compression ratio and a large combustion pressure. However, large combustion pressures generate high compression loads, which are repeated in the cylinder head gasket located between the cylinder block and the cylinder head, and result in contact between the hooks and the grommets made from a metal material. This contact generates a concentration of stress points, which can lead to the generation of cracks in the grommet rings.